1. Field of the Invention
The present invention relates generally to the art of making polyurethanes, and more particularly to the art of making polyurethane compositions suitable for fabrication by casting and curing in place.
2. Discussion of the Technology
U.S. Pat. No. 4,101,529 to Ammons discloses polyurethane compositions prepared from a cyclic aliphatic polyisocyanate a low molecular weight, active hydrogen-containing material and a polycarbonate diol which may be cast and cured in place to make articles in sheet form. The polyurethanes are prepared by mixing the polyisocyanate and the active hydrogen-containing materials together in a nitrogen atmosphere at temperatures between about 45.degree. and 90.degree. C. (about 113.degree. to 194.degree. F.). It is disclosed that where a catalyst is employed, a pot life extender such as stearyl acid phosphate should be used to facilitate casting the reaction mixture into a mold.
However, in some instances, such as casting the reaction mixture in contact with a polycarbonate surface, these reaction mixtures are unsuitable because the cure rate is too slow, allowing the isocyanate component to attack the polycarbonate surface.